1. Field of the Invention
The present invention relates to a method of monitoring communication flows carried across a network and hardware that implements monitoring, using such method. Particularly, the invention relates to such network monitoring method and hardware intended for efficiently collecting and analyzing the statistics data on packets per communication flow transmitted across a network that provides packet switching by using Internet Protocol (this network is hereinafter referred to as an IP network) in order to use such statistics data for charging and other administrative tasks.
2. Description of Related Art
Existing IP networks are administrated, based on a policy called a best effort: i.e., a network provides the best transmission performance that it can accomplish by using the maximum available resources for communication (for example, transmission bandwidth and delay time) in the network. As the IP networks conform to the best effort policy, the network provider does not practice the assurance of Quality of Service (QoS) indicated by, for example, a packet discard rate or packet transmission delay time measured for communication between terminals connected to the network. Therefore, it has not been implemented so far to monitor individual communication flow units (a data flow sent from a network user terminal and received at another network user terminal) and collect communication quality and related statistics data in the existing IP networks.
However, the role of the IP networks as general communications infrastructures has been established and communication services requiring a certain level of quality, such as sound/voice communications and visual communications across an IP network are prevailing. In this situation, a demand for the communication quality assurance in the IP networks is a growing tendency. The industry began to consider that common carriers charge users for IP network services provided by them, according to how much the user used what kind of service. In the above background, there are manifest demands for an IP network that ensures the quality of communication and for collecting statistics and transmission performance data used for confirming that the network actually provides services satisfying the quality of communication.
Monitoring traffic carried across a network and collecting statistics data thereof have so far been practiced, based on some technique of prior art, in order to promptly detect a congestion state and a fault occurring in the network, thus preparing the network for expanding its facilities and fault analysis. This traffic monitoring and statistics collection practice is such that items representing traffic particulars, such as the number of packets received, the count of bytes received, the number of packets transmitted, and the count of bytes transmitted are observed and measured per line interface on a packet switch (a router) for all packet switches that are components of a network, but communication quality per communication flow is not monitored. Statistics data obtained by observing the above items is stored into a Management Information Base (MIB) for storing management information, provided on each packet switch. Such a method of data collection is used that supervisory equipment existing in the network collects the information out of the MIB from all packet switches in the network and retains such information to be used for management.
With the demand for monitoring traffic per communication flow and collecting statistics data obtained by monitoring in the background, a few working groups of the Internet Engineering Task Force (IETF) are making study efforts to establish a method of measuring traffic carried across an IP network. According to the internet draft (draft-ietf-rtfm-architecture.txt) issued by the IETF, such measurement is taken by functional elements called meters 20 and 21 which are shown in FIG. 2, provided in the packet switches in the communication path. A functional element called a meter reader 22 collects the measurements taken by the meters 20 and 21. The monitoring system is architectured such that all packet switches as the components of the network are equipped with a meter, monitor communication flows, and acquire statistics data thereof. Network management equipment called a manager 23 performs the function of controlling the meters 20 and 21 and the meter reader 22. The statistics data on transmission performance collected by the meter reader 22 is analyzed by application software installed on the meter reader 22.
When an IP packet arrives at the meter 20, the meter 20 checks to see whether the IP packet matches any of the pre-registered communication flow conditions. A communication flow to which the IP packet belongs is identified by the match between the data, for example, source and destination IP addresses specified in the packet header and those pre-registered as the condition of the communication flow.
If such data existing in the header does not match any condition of communication flow, the meter 20 allows the IP packet to pass without executing any processing. If such data matches a communication flow condition, the meter 20 handles the packet, according to predetermined handling. Typically, handling is either measuring or ignoring. In the case of ignoring, the meter allows the packet to pass as does for condition mismatch. In the case of measuring, the existing values of the measurement items (e. g., the number of packets passed and the count of bytes passed) stored in the area for the communication flow to which the packet belongs in the flow table are updated by adding the count of the new arrival packet. The flow table is attached to each of the meters 20 and 21. Match/mismatch with a certain condition of communication flow is judged per packet. According to the result of this judgment, communication flow monitoring is performed and statistics data thereof is acquired. In this way, it can be implemented to monitor traffic and acquire detailed statistics data for each communication flow. The measured data is stored in the form of MIB and the meter reader 22 accesses the MIB and reads the data. From the meter reader, the manager 23 and an upper-level network management system linked thereto collect such data and the data can be used for charging and other administrative tasks.
As described above, by providing the intra-IP-network packet switches with the traffic measurement function and providing the network management equipment with the statistics collection function, monitoring of the communication flows that pass across the network is implemented.